An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Ambient Light Noise <s> In this paper, we implemented the outdoor Visible Light Communication (VLC) system based on Controller Area Network (CAN) which is normally used in a car, plane, ship, product line control system, medical device and industrial device. For vehicle to vehicle (V2V) or indoor vehicle communication, we used common use device such as head light and back light. We made an application circuit and explained the principle. Also, we found an outdoor VLC problem which is sun light noise and photo detector (PD) saturation problem. Circuit's pulse features were demonstrated by signal. Total communication distance was 20 m in the daytime outdoor condition and its experimental transmission performance is presented <s> BIB001 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Ambient Light Noise <s> An efficient optical filtering method for blocking outdoor light noise at visible light communication (VLC) systems has been presented. Unlike spread spectrum techniques or combining methods previously reported, the proposed method is very practical and efficient in that it uses an optical filter on the top of the photo diode to block obliquely incident unwanted lights, under the realistic assumption that light noise does not come into the photo diode directly. The experimental system demonstrates that the optical filtering method blocks nearly all light noise incident from an angle of 30° or higher. A simple pulse transmission over the VLC link also verifies the filter's blocking capability. <s> BIB002 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Ambient Light Noise <s> In this paper, a new design of visible light communication (VLC) receiver for on-off keying (OOK) modulation is proposed. The design is based on the cancelation of minimum offset voltage of the received OOK signal, using a novel minimum-voltage detection circuit. This circuit is capable of tracking the minimum voltage of an input signal even if its value increases with time. Experimental results show that the proposed receiver is immune to the interference from sunlight and indoor fluorescent lights. <s> BIB003 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Ambient Light Noise <s> An optical wireless communication (OWC) system based on a light-emitting-diode (LED) transmitter and a camera receiver has been developed for use in the automotive area. The automotive OWC system will require Mb/s-class data rates and the ability to quickly detect LEDs from an image. The key to achieving this is improvements to the capabilities of the image sensor mounted on the camera receiver. In this paper, we report on a novel OWC system equipped with an optical communication image sensor (OCI), which is newly developed using CMOS technology. To obtain higher transmission rates, the OCI employs a specialized “communication pixel (CPx)” capable of responding promptly to optical intensity variations. Furthermore, a new quick LED detection technique, based on a 1-bit flag image which only reacts to high-intensity objects, is formulated. The communication pixels, ordinary image pixels, and associated circuits (including 1-bit flag image output circuits) are then integrated into the OCI. This paper describes the design, fabrication, and capabilities of the OCI, as well as the development of the LED and image sensor based OWC system, which boasts a 20-Mb/s/pixel data rate without LED detection and a 15-Mb/s/pixel data rate with a 16.6-ms real-time LED detection. <s> BIB004
Similar to VLC, VLC based positioning is also vulnerable to the ambient light noise. The luminance of a typical LED is hundreds times lower than that of sunlight. The authors in BIB001 BIB002 showed that the PD became blind to LED when it was also exposed to direct sunligh. So far there is no effective solution for this problem. The author of BIB001 designed a simple light shield to conceal the PD from direct sunlight. In BIB002 , an optical filter was used to block all light coming to the PD at un angle of 30 • or above. A more sophisticated approach, which canceled out the voltage caused by the sunlight was proposed in BIB003 . With all these approaches, the angle of view of the PD should be small and the PD needs to be directed toward the LED. These approaches are impractical for positioning purpose since the PD must receive the signal from multiple LEDs and thus cannot point toward a specific LED. Compared to PD, image sensor does not suffer much from ambient light noise since the LEDs and the sun will be projected to different positions in the image. However, a strong light source can create haze and ghost in the image and thus detecting the position of the LED in the image would be more difficult. Besides sunlight, skylight is also an issue since the LED might not stand out from the sky background. Fortunately, LEDs might be installed on cars, bridges, or other dark backgrounds and this allows for the outdoor communication and positioning BIB004 .