Performance Analysis And Energy Efficiency Optimization Of Cooperative NOMA Communication System With SWIPT

In recent years,with the rapid development of wireless communication technology,the demand for spectrum efficiency has increased dramatically due to the explosive growth of data traffic and service.As a result,non-orthogonal multiple access(NOMA)has recently attracted widespread attention because it can provide high spectrum efficiency and achieve large-scale connectivity in fifth generation(5G)mobile communication networks.At the same time,with the rapid popularization of low-cost wireless devices such as sensors and relays,how to prolong the service life of these energy-constrained devices has also become a key problem to be solved.Because simultaneous wireless information and power transfer technology(SWIPT)has the characteristics of reliably obtaining energy from the source radio frequency signals,the combination of NOMA and SWIPT has been considered in cooperative networks.This combination can not only improve the spectrum efficiency,but also solve the life problem of energy-constrained devices.In this thesis,the performance analysis and energy efficiency optimization of cooperative NOMA communication system with SWIPT are studied as follows:Firstly,the performance optimization of multi-user single-relay cooperative NOMA systems with SWIPT is studied.The received SINR of users for decoding their signal is then analyzed for SWIPT-AF-NOMA,SWIPT-DF-NOMA and SWIPT-AF-TDMA communication systems,respectively.The optimization problem with the common throughput as the objective function is established.Then,the relationship among the common throughput,the power splitting coefficient,the output signal-to-noise ratio of the base station and the energy transfer coefficient for the above three kinds of communication systems is studied and compared by simulation.Simulation results illustrate that SWIPT-AF-NOMA system achieves the best performance.Secondly,the performance optimization of multi-relay multi-user cooperative NOMA system with SWIPT is investigated.In particular,three relay selection schemes are proposed based on the received SNR of users.The multi-relay communication systems with different relay selection schemes are compared with single-relay communication systems.Moreover,the relationship among the common throughput,the power splitting coefficient,the output signal-to-noise ratio of the base station,the energy transfer coefficient and the number of relays is analyzed through simulation.Simulation results demonstrate that the performance of multi-relay communication system is better than that of single-relay communicationsystem.The performance of relay selection scheme based on the best channel quality between base station and relays is obviously better than that of the other two relay selection schemes.It can be also observed that the system performance improves as the number of the relays increases.Finally,multi-user multi-relay system based on SWIPT-CR-NOMA is studied,where users are divided into a primary user and secondary users.A relay selection scheme based on the best channel quality between base stations and relays is applied.Then,under the condition of guaranteeing the communication quality for primary user,an optimization problem with common throughput as the objective function is formulated.Further,the relationship among the common throughput,the power splitting coefficient,the output signal-to-noise ratio of the base station and the energy absorption coefficient is investigated through simulation for different number of users.