Uncoordinated multiple access schemes for visible light communications and positioning

In visible light communication (VLC) systems, information are conveyed by visible light instead of radio-frequency electromagnetic waves. Based on received signal strength, accurate indoor positioning systems can also be built. Since a receiver obtains the superposition of signals from all light sources within line of sight together with ambient light, a multiple access scheme is necessary for the receiver to distinguish the received symbol and signal strength from each light source. This paper proposes two multiple access schemes for VLC. The first scheme supports information broadcast and positioning. By using 2^N timeslots, N transmitters transmit 2^N - 1 symbols in total. The second scheme supports positioning only but places emphasis on minimizing the required timeslots. In each 2N timeslots for an odd integer N, the channel gains of 3N - 1/2 transmitters can be estimated.