Research On Resource Allocation Algorithms For Wireless-Powered Backscatter Communication Networks

With the rapid development of wireless communication technologies,a bulk of interconnected wireless devices have been widely used in various fields of people's life.However,the limited battery capacities of wireless devices astrict their service life,which seriously affects the performance of communication networks.With the introduction of wireless-powered communication networks(WPCNs)and backscatter communications(BackComs),it is possible to solve the problems mentioned above.Specifically,WPCNs allow wireless devices to harvest the radio frequency(RF)energy from ambient electromagnetic environments first and then use the harvest RF energy for information transmission to reduce the dependence on the battery.BackComs allow devices to communicate by reflecting signals instead of actively generating signals,which significantly reduces the circuit consumption devices.Benefiting from the different requirements of WPCNs and BackComs for energy harvesting(EH)and data transmission,their combination can complement each other to improve transmission rates and energy utilization.Therefore,wireless-powered BackCom networks(WPBCNs)have excellent prospects in the future Internet of Things(Io T).However,the actual application of WPBCNs still faces many challenges,such as low transmission efficiency,low energy utilization,untimely data processing,and low-security performance.This thesis has carried out in-depth research on the resource allocation of WPBCNs in different scenarios.The main work is as follows:First,contraposing the low transmission efficiency of traditional BackCom networks,an optimal resource allocation algorithm for a multi-carrier WPBCN is studied.First,considering the cooperative transmission mode of BackCom mode and HTT mode,a system energy efficiency-based maximization problem is formulated by jointly optimizing the transmission time,reflection coefficient,transmit power,and EH coefficient,where minimum EH constraints and maximum transmit power constraint are considered.Then,the optimal solution is obtained via Dinkelbach's method,the variablesubstitution method,and the Lagrange duality method.Simulation results verify that the proposed algorithm has better energy efficiency and convergence compared with the existing algorithms.Second,contraposing the problem that the traditional BackCom network cannot cope with intensive data services,a resource allocation algorithm for multi-access edge computing(MEC)-based WPBCNs is studied.Considering the EH constraint,the maximum transmit power constraint,and task execution delay budgets,the total energy consumption of wireless devices is minimized by jointly optimizing the reflection coefficient,computation offloading coefficient,data offloading time,local computing ability,and user association.Then,an effective alternate iterative algorithm is designed to obtain suboptimal solutions via the alternate optimization(AO)method,the variablesubstitution method,and the interior-point method.Simulation results verify that the proposed algorithm has lower energy consumption compared with the existing algorithms.Third,contraposing the low-security and poor-robustness performance of traditional BackCom networks,a robust secure resource allocation algorithm for WPBCNs is studied.Considering a nonlinear EH model and the active artificial noise,a robust energy efficiency fairness problem is studied by jointly optimizing transmit power,artificial noise power,transmission time,and reflection coefficient,where the EH constraint and safe rate interruption constraint are taken into account.A suboptimal iterative algorithm is designed based on the fractional programming theory,the variable relaxation theory,and the AO method.The effectiveness and fairness of the proposed algorithm are verified compared with the existing algorithms.