Research On Indoor Visible Light Communication Technology Based On Non-Orthogonal Multiple Access

With the rapid development of the information industry and Internet industry,the market share of intelligent terminals is constantly expanding,which makes the pressure of traditional Radio Frequency(RF)business increasingly intensified,and spectrum resources are facing exhaustion,which is limited and non-renewable.Therefore,many scholars turn their attention to Visible Light Communication(VLC)technology,which is rich in spectrum resources and does not need authorization.However,because VLC uses LED with narrow modulation bandwidth as signal transmitter,the system capacity is severely limited.Therefore,the Power Domain Non-Orthogonal Multiple Access(PD-NOMA)technology is introduced into VLC system to effectively improve spectrum efficiency and amount of users through power domain multiplexing technology.Thus,this paper focuses on the application of PD-NOMA technology in indoor visible light communication system.Firstly,the channel model of indoor VLC system and PD-NOMA technology are analyzed briefly.Considering the non-cooperation among users,too strong background light,channel quantization error and other problems,it is difficult to obtain the perfect channel state information(CSI)from periodic pilot signal.Thus,model NOMA-VLC system under imperfect channel state information(ICSI)and analyze the reliability of system.Considering the lighting function of LED,the dimming control function is introduced into the system and the analysis on the reliability of this system is given.Secondly,in order to guarantee the quality of service(QoS)and improve the user performance experience,study on the power allocation scheme to maximize the system sum rate under single carrier ICSI NOMA-VLC system.On the one hand,through theoretical analysis,the power allocation formula is obtained by using Karush-Kuhn-Tucker condition.On the other hand,particle swarm optimization(PSO)is proposed for flexible power allocation The simulation results show that the proposed power allocation schemes can effectively improve the system performance when the users rate is not lower than the minimum reachable rate.Finally,study on the system resource allocation under the multi-carrier ICSI NOMA-VLC system.Two resource allocation schemes are proposed to optimize sum rate:(1)divide the resource allocation problem into two sub-problems of user grouping and power allocation.According to the existing research foundation and indoor visible light communication system characteristics,an improved KM algorithm is proposed to group users according to the difference of users' channel gain,and a Full Search Power Allocation(FSPA)scheme with optimal performance is adopted within the group.(2)Nested particle swarm optimization is proposed to solve the resource allocation problem directly.The simulation results show that when the number of users in the group is 2,the two resource allocation schemes can greatly improve the system performance compared with the common orthogonal multiple access schemes.At the same time,the nested PSO algorithm can also be applied to the optimization problem with a large number of users in the group.