Research On Multi-users Network Model And Its Networking Scheme For Indoor VLC Systems

Recently, developments in the materials and devices of solid-state light emitting diode(LED) predict that white LEDs will serve as the dominant lighting source in the future. Because of its advantages such as large capacity, without frequency applications, anti-magnet interference, enhanced security, low cost etc., visible light communication(VLC) based on LEDs has attracted more and more attentions. In order to construct indoor VLC networks, the reasonable full-duplex communication mode is important. Some scholars propose that the infrared radiation can be used as the medium for the uplink to avoid the interference between uplink and downlink. It may be effective for fewer user, but for multi-users(especially dynamic multi-users) VLC networks, multi-users access interference(MUAI), and user reception interference(URI) caused by visible light downlink will become more significant.In this paper, aiming at the key issues such as full–duplex communication quality and multi-users networking, a novel VLC network model and its networking scheme are studied in detail. Firstly, in order to make full use of the spectral efficiency of the infrared light and eliminate the interference of the infrared links among multi-users, we propose the “multi-wavelengths-space management” theory to manage the mobile multi-users indoors. The theory defines the management principle that the user’s uplink is managed by the terminal having the same infrared wavelength and its downlink is done by the terminal when the user locates in this terminal’s VLC coverage. Secondly, we set up a multi-transceivers illumination/communication terminal structure, on which a certain number of infrared receivers with the same wavelength are integrated in all directions. Because the terminal size is limited, all the available infrared wavelengths are integrated on several terminals. Meantime, we outline optimal designs of such multi-terminals layout such that illumination is uniform and URI is eliminated(i.e. the VLC overlapping area is eliminated). Thirdly, we propose a modified CSMA/CA method to improve the bandwidth utilization ratio of visible light and inhibit MUAI. Based on the above basis, we present routing strategies about the user access network and the link establishment between users. We also present network performance in aspects of access collision probability, throughput, access time and link establishment time. Finally, we make the relevant numerical simulations. The results show that ourproposed networking scheme and routing strategies are effective and feasible in indoor multi-user VLC networks.