User-QoE-based Access Strategy Of Indoor Visible Light Communication System

As a candidate wireless Communication technology in the future,Visible Light Communication(VLC)is a technology that combines Communication and lighting deeply,which can not only provide green lighting,Moreover,it can provide high-speed data transmission without filling the existing Radio Frequency(RF)spectrum resources,also can reduce the burden of the existing wireless communication system.However,in a VLC network indoor scenario,it is not easy for the User Equipment(UE)to connect to the appropriate Light Emitting Diode(LED)to achieve a satisfactory quality of service.A series of factors,such as the number of users,coverage probability and receiving perspective,will affect the access of users.In this paper,the Quality of Experience(QoE)is introduced as the system performance index,and the visible light communication system based on non-orthogonal Multiple Access(NOMA)is designed.Based on the NOMA probability coverage model of QoE,a greedy access algorithm based on user QoE optimization is proposed in the scenario of single control center of the system,and the user decision access strategy is proposed in the scenario of multiple control centers combined with the user matching method.Compared with Proximity Access Algorithm(PA),the greedy Access Algorithm has high system stability,large proportion of Access users,excellent average user experience and good fairness.The main work and innovation points of this paper are as follows:1.Aiming at UE as the center,this paper introduces QoE as the system performance index.UE-centered QoE and network-centered Quality of Service(Qo S)are not the same,Qo S is from the perspective of the network to use a variety of basic technology for business management,it only reflects the performance of the network transmission level,in terms of UE's recognition of the Service is not directly reflected;However,QoE is a standard evaluation index based on UE recognition degree,which reflects higher degree of UE's satisfaction with network service than Qo S.This paper adopts NOMA multiple access mode.NOMA allows multiple users to utilize all available frequency and time resources at the same time,which greatly improves the spectrum efficiency of the system.Due to the short distance between LED and photo-diodes(PDs)and line-of-sight(LOS)transmission,the signal-to-noise ratio of VLC link is high,while NOMA in the power domain performs better in the case of high signal-to-noise ratio,and the channel of VLC is relatively stable,which is conducive to the power allocation of NOMA.Therefore,this paper proposes the NOMA probability coverage model of QoE,and on this basis,takes UE as the center to consider the overall performance of the network,optimizes the access mode of UE in the VLC system,so as to improve the UE experience quality.In this paper,a probability coverage model of QoE is proposed,which defines that there is a certain probability that the UE in the coverage area of LED projection can have a satisfactory QoE,and the QoE is used as the system performance evaluation index.2.The QoE Optimized Greedy Access Algorithm(QGA)based on user QoE is proposed in the scenario of a single control center of the system,which is compared with the PA algorithm which takes distance as the only priority.Simulation results show that QGA has better performance in terms of average UE experience quality,access UE proportion,fairness,system robustness and so on.3.Based on NOMA's QoE probability coverage model,the UE decided access algorithm in multi-control center scenaior(UAC)is proposed.However,NOMA simultaneously serving multiple UEs will cause co-channel interference,which is especially serious in a small cell.Therefore,when NOMA is used in a VLC system,it is difficult to process a large number of UEs at the receiver side simultaneously.The Orthogonal Multiple Access(OMA)and NOMA are combined to pair and group the UE in the data coverage,so as to enhance the user experience and improve the system capacity.The simulation results show that,compared with the performance of VLC system with single control center,the average quality of UE experience is slightly better in the case of multiple control centers,although the proportion of UE that can access the system is slightly smaller.