Research On Resource Allocation In Backscatter Communication Networks Based On Energy Harvesting

With the rapid development of wireless communication,massive wireless devices access networks,which brings serious energy consumption.In addition,due to limited battery capacity,the energy of many wireless devices is finite.It is also inconvenient to replace or recharge batteries.Backscatter communication networks based on energy harvesting(EH)can help wireless devices get rid of batteries,reduce energy consumption and enhance users’ service experience,and thus they have attracted wide attention from academic and industry.In the backscatter communication networks based on EH,when massive wireless devices access these networks,non-orthogonal multiple access(NOMA)technology can be integrated into these networks to support simultaneous information transmission of multiple wireless devices,which improves the spectrum utilization efficiency as well as the network throughput.In order to give full play to the advantages of backscatter communication networks based on EH and NOMA,there are still some key problems that need to be addressed.First,when users perform the selection optimization between backscatter communication and active radio transmission,both the resource allocation problem and the interference problem need to be considered.Second,backscatter communication is always appropriate for short-distance communication,which fails to meet the users’ requirement of long-distance communication.Third,when the high building is located between the radio frequency(RF)signal source and the user,the information transmission of the user will be interrupted.Therefore,according to these problems,some key technologies such as cognitive radio(CR),relay transmission and intelligence reflecting surface(IRS)are introduced into backscatter communication networks based on EH and NOMA.In such networks,both network performance and users’ service experience can be enhanced by properly allocating resources.The main contributions and innovations of this thesis are as follows:1.In backscatter communication networks based on EH and NOMA,the interference problem is deeply studied,a communication mode selection and resource allocation strategy based on interference-aware is proposed.First,the CR technique is introduced into backscatter communication networks based on EH and NOMA to improve spectrum utilization efficiency.Second,the transmit power of secondary users can be controlled by reasonably allocating the time resource among EH,backscatter communication and active radio transmission,which meets the interference constraint requirement of the primary user.Third,a convex optimization problem is formulated with the goal of maximizing the throughput of secondary system by jointly considering the interference constraint requirement of the primary user and the time resource allocation among EH,backscatter communication and active radio transmission.The Lagrangian multiplier iterative algorithm is utilized to solve this problem and obtain the optimal time resource allocation.Finally,simulation results demonstrate that the proposed strategy can significantly improve the throughput of the secondary system by comparing it with other two benchmark schemes.2.In backscatter communication networks based on NOMA,the problem of limited communication range is deeply studied,a cooperative communication and resource joint optimization scheme based on simultaneous wireless information and power transfer(SWIPT)is proposed.First,both relay transmission and SWIPT technologies are integrated into backscatter communication networks based on NOMA,which enables all relays to simultaneously help users transmit information based on harvested energy,so as to improve the communication range as well as the network throughput.Second,a non-convex optimization problem is formulated with the goal of maximizing the network throughput by jointly considering the power-splitting(PS)of relay and the time resource allocation among backscatter communication,EH and relay transmission.To decrease the complexity of solving this problem,it is decomposed into two sub-problems,and an iterative algorithm based on joint optimization of PS coefficient and time allocation is proposed to obtain the maximum network throughput.Finally,simulation results demonstrate that the proposed scheme can significantly improve network throughput by comparing it with two benchmark schemes.3.In backscatter communication networks based on EH and NOMA,the non-line-of-sight transmission problem is deeply studied,an IRS assisted communication and resource management mechanism based on energy efficiency optimization is proposed.First,the IRS technique is integrated into backscatter communication networks based on EH and NOMA to help the base station communicate with the cell edge user,which improves the channel condition of the cell edge user as well as the communication range of these networks.Second,the optimal PS coefficient of backscatter device is obtained based on the harvested energy and the energy consumption of backscatter communication.Third,an optimization problem is formulated with the goal of maximizing the energy efficiency by jointly considering the phaseshifts of IRS and the power allocation of NOMA users.To decrease the complexity of solving this problem,it is decomposed into two subproblems,and the Dinkelbach-based iterative algorithm is utilized to solve this problem and obtain the maximum energy efficiency.Finally,simulation results demonstrate that the proposed mechanism can significantly improve energy efficiency as well as network throughput.