Dynamic spot diffusing configuration for indoor optical wireless access

This paper introduces the dynamic spot diffusing (DSD) configuration for high-speed indoor wireless optical communications. In this configuration, data are modulated onto a moving spot which is translated over the ceiling. A multi-element imaging receiver is pointed upward and acquires data whenever the transmitter spot is in its field-of-view (FOV). We develop expressions for the channel capacity of such DSD links and discuss design techniques to maximize these information theoretic bounds. Rather than tracking the transmitter spot, we apply rateless erasure correcting codes to approach the capacity of the simulated DSD links. This technique is demonstrated to have better flexibility, greater multipath immunity, higher data rates and simpler transmitters than previously defined multi-spot and diffuse architectures. In a 6 x 6 x 3 m room, simulated data rates vary between 7 Mbps to 25 Mbps at different positions using a single 100 Mbps transmitter and between 35 Mbps to 84 Mbps using 6 spots and the designed erasure correction code. Using power efficient modulation and power gain due to the spot motion of the DSD system, proportionally higher rates are estimated when faster 1 Gbps and 10 Gbps transmitters are employed.