Research On Multi-user Downlink Optimization Method For Indoor VLC-WiFi Heterogeneous Networks

Compared with the traditional radio frequency(RF),visible light communications(VLC)has the advantages of large bandwidth,high data rate,green energy saving,no electromagnetic interference,and so on.VLC uses light emitting diode(LED)as light source,carries information through high-speed flashing signal,and takes communication into account while lighting.However,the coverage of a single VLC access point(AP)is small;the uplink communication relies on the light-emitting devices at the receiving end,which is easy to cause eye discomfort;the VLC communication is easy to be blocked,resulting in communication link blocking.In the indoor environment,in order to make up for the shortcomings of VLC uplink communication,Wi Fi devices are widely installed in various communication terminals,without additional communication charges,and become the best "partner" of VLC networking.However,there are two problems that cannot be ignored because of the dense coverage of multiple APs in VLC-Wi Fi heterogeneous networks.Firstly,it is difficult to select AP access in multi-user downlink.Secondly,the interference in multi-user downlink is becoming more and more serious.In order to optimize the throughput and user experience of the communication system,the AP access point selection and interference management of the indoor VLC-Wi Fi multiuser downlink are studied.In the third chapter,a novel two-step optimal greedy matching(TSOGM)algorithm based on bipartite graph is proposed.In TSOGM algorithm,through the design of user and AP selection preference,decision-making user and AP two-way selection process,which may help us to find a performance compromise between the system and users,and find the best AP access for users.The simulation results show that the proposed algorithm optimizes the throughput and the fairness between users in the VLC-Wi Fi heterogeneous networks compared with comparison algorithm in different layout.In order to solve the problem of interference management in indoor VLC-Wi Fi heterogeneous networks.In chapter 4,an elite user clustering subchannel allocation(EUCSA)algorithm is proposed.In EUCSA algorithm,firstly,considering the characteristics of VLC network that is easy to be occluded and interfered,we put forward the Wi Fi access criteria of interrupt user and interference source user.Secondly,considering that the users in the remaining VLC network are vulnerable to inter cell interference,an elite user clustering criterion based on the coverage graph of the transmitter and the conflict graph of the receiver is designed to optimize the SNR of users.Finally,considering the resource competition of multi-user downlink,different subchannel allocation algorithm is designed for VLC-Wi Fi networks in this thesis.Simulation results show that EUCSA we proposed improves system throughput and optimizes satisfaction of users compared with benchmarks in different layout.