Research On MAC Access Mechanism In Visible Light Communication Network

White LED can build the network coverage when it is used as a light. This technology need not compete the electromagnetic spectrum and has advantages in no electromagnetic interference, safety and energy saving. This paper researches on the indoor visible light communication channel characteristics, analyzes the factors that affect the transmission model, also designs an effective MAC access mechanism to solve the hidden terminal problem and uplink and downlink by different LED management in the visible light network.Firstly, the white LED is simulated by the Lambert radiation model, and the radiation characteristics are analyzed under the different LED light half-power angle. Based on the analysis of the channel characteristics, the channel impulse response of a single light source and the distribution of illumination of multiple LED arrays is simulated and analyzed in a particular indoor environment. Secondly, the slotted random access algorithm of the visible light network protocol IEEE 802.15.7 is simulated in many aspects, including the node number, backoff exponent and backoff number's influences on the network throughput and average delay. Finally, in the network configuration of the indoor multiple LED arrays, the way using an infrared as uplink and visible light as downlink to build a network eliminates the interference between the links. For indoor visible light communication network hidden terminal and the problem of uplink and downlink managed by different LED, this paper proposes to add multiple forwarding RTS/CTS mechanism and analyzes the improved protocol performance to verify the reasonableness on the existing 2D Markov model.This design of the protocol comply with the characteristics of visible light communication. According to multiple nodes in the network, the protocol effectively reduces the collision probability and has a good network throughput performance.