An Experimental Validation of Angular Diversity Aperture (ADA) Receiver in MIMO VLC Systems

In an Angular Diversity Aperture (ADA) receiver, each photodiode in the receiver is placed below an opaque screen with a transparent aperture. Angular diversity is achieved by using different offsets between each photodiode and the corresponding aperture. In this paper, experimental results are presented for the channel gains of each receiving element as the position of the receiver changes relative to the transmitters. These results demonstrate why the ADA achieves a well-conditioned channel matrix. Experiments were also performed for a multiple-input multiple-output (MIMO) configuration using two transmitters and three receiving elements. The transmitted signals were modulated using asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM). Bit error rate (BER) results were presented for a range of receiver positions and orientations relative to the transmitters. These results show that the ADA receiver would work in a typical visible light communications scenario, where the receiver in a mobile portable device moves relative to the transmitting lights. In comparison, the BERs for the conventional receiver using bare photodiodes were also measured. The results demonstrate the importance of angular diversity in MIMO optical wireless communications and show that the ADA receiver achieves this in a simple compact structure.