LightTour: Enabling Museum Audio Tour with Visible Light

Lennert Vanmunster, Jona Beysens, Qing Wang, Sofie Pollin

Abstract: We exploit visible light in museums to design LightTour, a wirelessly networked system empowered by visible light that provides audio tour service to visitors. LightTour supports full-duplex transmissions with a single multi-band optical receiving antenna at each transceiver: for the downlink, the access points (APs) broadcast audio streams to visitors' devices through visible light communication; for the uplink, the devices send visitor's feedback to APs through infrared light transmission. To network a number of APs and devices, we identify two main challenges: (1) self-interference at the APs, caused by the floor reflection of their downlink signals, that degrades uplink transmissions; (2) the uplink hidden-device problem. In this work, we develop an online low-complexity method that can achieve maximally 30 dB self-interference cancellation at APs. We design a new MAC protocol - full-duplex carrier sense multiple access with collision detection & hidden avoidance (FD-CSMA/CD-HA) - to solve the hidden-device problem and to provide reliable and high-throughput audio broadcasting. To evaluate the system performance of LightTour, we build a prototype with off-the-shelf components. Besides, we develop a simulator to assess large-scale scenarios. The results validate our self-interference cancellation method's feasibility and demonstrate FD-CSMA/CD-HA's robustness and its advantage over existing protocols.