Selective switching dual-transmission scheme in multi-LED Hybrid VLC-P2P networking system

In this paper, we propose a technique to solve the physical interference phenomenon occurring in the hybrid VLC-P2P network system Visible light communication (VLC) utilizing indoor lighting infrastructure is advantageous for establishing a wireless peer-to-peer (P2P) network environment. However, unlike RF wireless network environments, adjacent lighting and the optical wavelengths of multiple light sources cause interference among one another, greatly degrading the performance of the network system. In an actual indoor environment in which a plurality of lights exist, the received signal power differs for each LED according to the position of the receiver, and the LEDs interfere with each other. In addition, since each LED light source has a narrow field of view (FOV), the receiver located at the cell boundary receives increased interference. Since the visible light communication system uses the IM-DD system, the system performance is significantly degraded from such interference. To solve this problem, we propose selective switching dual –transmission (SSDT) for a multi-LED-VLC system. The proposed scheme can divide the received power range into three areas of the cell where the receiver is located. These include: area 1, where the target receiving signal power range is largest; area 2, where the range of interference signal power of adjacent LED is large; and area 3, where the received power occurs at cell boundary. Therefore, the receiver detects a signal having a different received power according to the receiver position in the current cell. If the target signal has the largest received power, it is used as it is. If interference signals from adjacent LEDs are detected, the interference cancellation technique using the difference in received power is used to eliminate the interference. If the receiver is located at the boundary of the cell, it becomes difficult to distinguish the interference signal component of each LED, so each LED is switched to cooperative communication. Through this scheme, the performance of the whole VLC-P2P network system can be improved by selective transmission according to the position of the receiver.