A study of shadowing on indoor visible-light wireless communication utilizing plural white LED lightings

White LED is considered as a strong candidate for the future lighting technology. We have proposed an optical wireless communication system that employs white LEDs for indoors wireless networks. In this system, LED is not only used as a lighting device, but also used as a communication device. The system has large optical power and large emission characteristic at the transmitter to function as a lighting device. The system has a specific delay profile different from the infrared wireless communication. In this paper, we discuss the shadowing effect on the system utilizing plural LED lightings including the performance of ISI based on the delay profile. We consider the downlink transmission based on TDMA and evaluate the shadowing effect caused by pedestrians with computer simulation. As a result, when the shadowing often occurs at 800 Mb/s, the performance of outage call duration rate and blocking rate are improved by the 3 LED lightings resulting in an optical number of the LED lighting. We show that the system with the optimal number of the LED lighting is robust against shadowing and can accommodate more calls.