Collaborative Transmit Power Adaptive Optical Wireless System for an Indoor Channel

Abstract

We propose a novel optical wireless (OW) system based on power adaptive multi-beam spot diffusing transmitter serving multiple 7-segment MRC angle diversity receivers. A feedback link is assumed between the transceivers so that the receiver conveys to the multi-beam transmitter the new beams transmit power weights to be used in order to achieve the best signal quality at a given receiver location. The performance of a sample case of three receivers placed in different configurations in the room is evaluated in terms of signal-to-noise ratio (SNR) and is compared with the single receiver scenario with and without a power adaptation. In the presence of one receiver, the transmit spot powers can be adjusted for optimum performance at that receiver location. For multiple receivers, there is conflict and we propose spot power adaptation based on the average requirements (power distribution in spots), i.e., EGC of spot power or MRC combining of spot powers. The results showed that the three receivers benefit most from an adaptive transmitter when each is placed at a corner of the room. In this case, as much as 2.8 dB increase in SNR is achieved for all three receivers at the corners. Moreover, a considerable SNR gain (1.8 dB) is also obtained when all receivers lie directly under the line of diffusing spots. Although the performance of the collaborative transmitter when all three receivers were located near room wall produced very minimal improvement, none of the receivers suffered any decrease in SNR.