Research On Throughput Optimization Of Wireless Powered Backscatter Communication Network With Transmission Fairness

With the rapid development of 5G and the Internet of Things(Io T),a large number of wireless devices are connected to wireless communication networks.Traditional power supply methods will not be able to meet future communication needs,and it is urgent to provide sustainable energy supply for energy-scarce networks.Therefore,Wireless Powered Communication Networks(WPCN)and Backscatter Communication(BC)will become two key technologies in the future Io T field.Among them,WPCN can support long-distance information transmission of energy-constrained devices.However,it takes a certain amount of time to obtain energy before each information transmission.BC reflects information in the form of instantaneous excitation by RF signals,and basically does not need time to obtain energy,and the energy consumption generated by passive transmission is very low.However,the transmission rate of BC is low,and because it relies on the indication of the incident signal,it has poor initiative.Therefore,in this thesis,to achieve the goal of balancing system fairness and throughput optimization,BC and WPCN are jointly designed to construct Wireless Powered Backscatter Communication Networks(WPBCN),fully combining the advantages of the two,and analyzing the problem of optimal allocation of resources in the WPBCN system.The following are the main research work and innovations of this article:In order to solve the unfair problem caused by the "double near-far problem" of traditional doublehop WPCN,and to make up for the system capacity lost due to fairness considerations,this thesis introduces BC into the traditional double-hop WPCN and proposes a new double-hop WPBCN network.In this network,when one relay collects energy from the HAP,the other relay will backscatter part of the corresponding user's data to the HAP,and vice versa.Subsequently,the two relays use the harvested energy to amplify and forward the remaining data to the HAP.With the goal of maximizing the common throughput,this thesis proposes a time optimization algorithm suitable for double-hop WPBCN networks,and calculates the approximate optimal solutions of the network relays' backscatter time,energy harvesting time,and information forwarding time respectively.Finally,the simulation data shows that compared with the single mode,this scheme can further improve the system throughput under the condition that fairness is guaranteed.Although the dual-hop WPBCN network can consider fairness and throughput optimization at the same time,the system settings of two users limit its wide application in practice.Therefore,this thesis extends from the two-user double-hop WPBCN network to the multi-user universal situation,and expands the scope of application of WPBCN.In this system,when a certain wireless device performs backscattering,other wireless devices can harvest energy at the same time.Backscattering and information transmission are allocated to two different time slots by TDMA.The entire time period is fully utilized to reflect or transmit information,which effectively improves the time utilization of the system.In order to consider throughput optimization and fairness issues in a balanced manner,this thesis proposes a minimum throughput maximization criterion,which converts the original nonconvex problem into a convex optimization problem by introducing additional variables,and then calculates the closed-form solution of the optimal time allocation.The simulation results verify that compared with the scheme that combines BC and WPCN but does not consider fairness and the scheme that considers fairness but only WPCN,the method proposed in this thesis can not only ensure better user fairness,but also achieve higher system throughput.