A new design of light source arrangements for indoor visible light communication

A new design of light source arrangements for indoor visible light communication is proposed in this paper to obtain uniform lighting conditions and stable communication performance. The models of illuminance and received signal to noise ratio are established in a room. The room size is 5 m×5 m×3 m. A 2-factor of signal to noise ratio distribution is introduced to evaluate the fairness of the whole system to all users. LED array filled with LEDs with transmitted power as small as 20mW now is often used in indoor visible light communication as the light source. The distribution of illuminance shows that the LED arrays can supply sufficient illuminance but the standard deviation is very large. The fluctuation of the received signal to noise ratio distribution is strong, which is disadvantageous for communication. The values of illuminance under the LED arrays source conditions are big while the values are very small in the edge region of the room. In view of this situation we propose to place individual LEDs with transmission power of 1W evenly on the ceiling instead of LED arrays. The interval is 0.5m and the results show that the standard deviation of illuminance is decreased but the illuminance at some locations is too small to satisfy the lighting requirements. So we optimize the design and replace the 1W LEDs at the edge of the room with 2W LEDs while the interval remains the same. It turns out that the standard deviation of the illuminance has a reduction of 63.2% compared with that using the LED arrays as the light source. Meanwhile the 2-factor under this source arrangement has been increased by a factor of 2.08 compared with that under the LED arrays source conditions.