Adaptive Beam Clustering Optical Wireless System for An Indoor Channel

The separating distance between the transceivers is one of the main factors that affect the quality of the received optical signal as the receiver changes locations in an optical wireless (OW) system. A beam clustering method was proposed to improve the indoor OW channel´s performance by combating the degrading effects of multipath reflections. The method involved transmitting binary data bits over two other clusters of beams aimed at walls in addition to the one aimed at the ceiling. In this work, we investigate a novel approach to further improve the signal quality on reception using a proposed adaptive transmitter composed of three spot diffusing sub-transmitters aimed at the same three directions as in the beam clustering method. The receiver communicates with the transmitter and sends tap weights (for transmit powers) to be used by the sub-transmitters which optimises the signal reception based on the initial received pulses at different locations. Performance comparison with results of a non adaptive transmitter system is presented in terms of signal-to-noise ratio (SNR), delay spread (DS) and path loss distributions for two receiver types: 1) a single detector wide field-of-view (FOV) receiver and 2) a multi-detector angle diversity receiver. Our results show a significant improvement achieved with an SNR gain of 18 dB compared with the conventional diffuse system and a 6 dB SNR gain without transmitter adaptability. Therefore, at the expense of moderate computations, the use of an adaptive multi-beam clustering transmitter is promising and can enhance the optical signal reception to suit user mobility requirements.