Effect of driving current on phosphorescent white LED and a second-order hardware pre-equalization strategy for VLC in military vehicle

Abstract

Phosphorescent white Light Emitting Diodes (LEDs) serving as military vehicle lighting sources have great potential for high-speed communications. Considering the light intensity, driven by LED's driving current in military vehicles, varies with the combat mission, this paper starts with analyzing the driving current's effect on phosphorescent white LED performance in two cases: LED with and without blue filter. We conclude that photoelectric characteristics and frequency response of LED without blue filter are steadier to the driving current's fluctuation. In view of good lighting and reliable communication, we argue that blue filter is not conducive to visible light communication (VLC) in the military vehicles. Comparing to phosphorescent white LED with blue filter, we observe that the one without blue filter has higher frequency severe attenuation and lower -3 dB bandwidth, which blocks its high-speed transmission application. For that, we put forward a new second-order hardware pre-equalization strategy, and the experiment results demonstrate that the -3 dB bandwidth of 1W phosphorescent white LED without blue filter can be extended from 3.8 MHz to 93 MHz, which allows 236 Mbps transmission rate with Bit Error Ratio (BER) less than 3.8×10−3 in 1.5 m by Non Return to Zero-On Off Keying(NRZ-OOK) modulation technology and meets the military intra-vehicle communication requirement in this paper.