As an alternative technology to radio-frequency-based communication, visible light communication(VLC) has attracted tremendous interest from both academia and industry. For its medium access control (MAC) protocol, most existing design has focused on the half-duplex mode, which can be inefficient for two-way communications. In this paper, we propose a novel full-duplex MAC protocol for VLC networks. Different from half-duplex operation, full-duplex operation allows concurrent sending and receiving of data frames between the central node and terminal nodes. We show that under certain scenarios, it can achieve almost threefold downlink throughput from the central node to terminal nodes as compared with half-duplex operation.
Unfortunately, owing to asymmetric traffic demand on the uplink and downlink, full-duplex transmission cannot always be realized. To increase the probability of full-duplex transmission, we further propose a self-adaptive minimum contention window full-duplex MAC protocol that can significantly increase the probability of duplex operation. Our experimental study shows that the proposed MAC protocol can effectively mitigate channel collisions and achieve significantly higher system throughput.