Realization And Optimization Of Visible Light Communication Network With Multi-user Dynamic Access

Visible Light Communication(VLC)technology has become an important choice for ultra-dense networks due to its advantages of large bandwidth and easy deploy-ment.Combining the characteristics of visible light communication,designing and im-plementing a mobile VLC network is important for practical applications.The research of this paper mainly include:the research of communication network platform of LiFi hybrid WiFi in indoor mobile environment,and the research of delay-aware resource allocation for indoor VLC-OFDM network.Firstly,we studies the indoor VLC network platform of LiFi hybrid WiFi.Visible light is only suitable for downlink transmission.In this paper,WiFi is used as the up-link transmission mechanism,we present a preliminary design of a hybrid networking architecture using downlink VLC and uplink WiFi that supports dynamic user access and resource allocation.Considering the user movement,we design a suitable LED lay-out scheme according to the half power angle of the LED.Extensive measurements are conducted to select the optimal operating point of LED,including the LED DC voltage bias,and the best symbol rate of downlink.In such a network,a cental coordinator is employed for user access,lamp selection and resource allocation.The interference from adjacent cells is mitigated based on the time-division(TD)mechanism,and a flexible access for mobile users can be achieved.Moreover,the proposed VLC/WiFi hybrid net-working is realized with FPGA.Experimental results show that the bit error rate(BER)of the real-time network is 6.3091 x 105,and the frame loss rates(FLRs)of mobile user are about 8.2%,which meets the mobile communication requirements.Then,we presents a delay-aware resource allocation for indoor VLC-OFDM net-work.Most services have certain delay limits.We combines VLC network physical layer(PHY)layer channel information(CSI)and media access control layer(MAC)layer Queue Status Information(QSI)to get a joint resource allocation scheme for cross-layer optimization.Based on the ultra-dense LED layout and orthogonal frequency division multiple access.Considering the Low frequency cutoff of VLC channel,the transmitting power constraint of the LED and the coordinated transmission of multiple users.The joint optimization problem becomes an aggregated Markov decision process(MDP)problem.Which is difficult in determining the optimal policy because of its huge state space.So we reduce the state space by load balancing,fixed user resource slicing.The simulation results show that the proposed scheme is much better than the Round-Robin scheduling joint water filling scheme.