For study on the channel characteristics using white LEDs, the basic construction of communication system and the principle of impulse response using ray tracing are analyzed. And then, the simplified ray tracing is proposed to calculate the channel impulse response, this method only considers the reflections within three times. Finally, numerical simulation proves the feasibility and efficiency of this method. The simulation results show that the system impulse response is with the direct and the first reaction as the main component, and var...