Channel capacity optimization for an integrated wi-fi and free-space optic communication system (WiFiFO)

Recent advances in free-space optical technology promise a complementary approach to increasing wireless capacity with minimal changes to the existing wireless technologies. This paper puts forth the hypothesis that it is possible to simultaneously achieve high capacity and high mobility by developing a communication system called WiFiFO (WiFi Free space Optic) that seamlessly integrates the recent free- space optics technologies and the current WiFi technologies. We briefly describe the WiFIFO architecture then discuss the main contribution of this paper that is optimizing the capacity of the proposed WiFiFO system. Specifically, we consider the problem of power allocation for multiple FSO and WiFi transmitters in order to achieve maximum system capacity for given budget power. A mathematical model of the combined capacity of FSO and WiFi channel is derived. We show that the power allocation problem for WiFiFO can be approximated well as a convex optimization problem. To that end, an algorithm based on gradient decent method is developed. Simulation results indicate that the proposed algorithm, together with system architecture can provide an order-of-magnitude increase in capacity over the existing WiFi systems.