Research On Hybrid Link Technology Based On WiFi And Infrared In Indoor Visible Light Communication System

Because of without frequency application, anti-magnet interference, enhanced security, high transmission rate, etc., the visible light communication(VLC)has attracted more and more attention, which makes VLC develop rapidly. At present, the research of indoor VLC technology is mainly focused on improving the modulation bandwidth of LED and using LED to provide high speed downlink of mobile terminal.One of the major technical problems in VLC is how to effectively establish the uplink of mobile terminal. In this thesis, an uplink scheme of combining the Wi Fi with infrared is proposed. The proposed uplink scheme can make full use of the spectrum resources of existing Wi Fi and infrared, also can make up for the deficiency of single uplink scheme, which allows users in good communication condition, also increases the system capacity and decreases the access delay.Firstly, in order to solve the problem of how to select the access point when users enter indoor VLC system, we combine the AHP method with SAW method as the solution to choose the access point. Secondly, for the problems of network congestion and access delay increase caused by multi-users choosing the same access point, a theory of ?virtual switch? is introduced, which means that the users dynamically compares the size of the obtained backoff time by collision and channel occupied time by other users, and then make the choose which access point should be accessed. Finally, we calculate and analyze the collision probability, access delay and system throughput. Simulation results show that the proposed uplink system and the access solution can solve the problem of multi-user access in indoor VLC, and that the proposed method is applicable and feasible.