Research On Rate Splitting For Intelligent Reflecting Surface-Assisted CR-NOMA Systems

With the substantial increase in the number of various Internet of Things devices and the rise of wireless applications,how to effectively improve the capacity and spectrum utilization of wireless communication networks has become a hot spot of concern.To address the above problems,rate splitting(RS)technology and intelligent reflecting surface(IRS)are proposed as key technologies to effectively improve spectrum utilization and energy utilization.Compared with traditional multiple access technologies,such as non-orthogonal multiple access(NOMA),RS technology can more flexibly reach the capacity zone of the uplink multiple access channel.In addition,the IRS can not only expand the signal coverage by controlling the propagation environment of the signal,but also have the advantage of low energy consumption.Therefore,the combination of these two technologies can greatly improve the system performance of uplink cognitive radio(CR)NOMA(CR-NOMA).This thesis mainly focuses on the two key technologies of IRS and RS,which study the outage performance of the secondary user(SU)in the uplink CR-NOMA system.The main research content and main contributions of this thesis can be summarized as follows:First,this thesis proposes an RS scheme for the outage performance optimization problem of a single IRS assisted uplink CR-NOMA system,which effectively improves the outage performance of SU.By deploying the IRS between the primary user(PU)and the base station(BS),the tolerable interference threshold of the PU is improved.Then,this thesis considers the channel gain of IRS to PU,and jointly optimizes and designs the optimal transmit power allocation,target rate allocation and successive interference cancellation(SIC)decoding sequence.Subsequently,this thesis simulates the outage performance of the proposed single IRS-aided uplink CR-NOMA system.The simulation results show that the RS technology proposed in this thesis greatly improves the outage performance of SU in CRNOMA system compared with the uplink CR-NOMA system without RS technology.Secondly,this thesis extends from a single IRS-assisted uplink CR-NOMA system to multiple IRS-assisted uplink CR-NOMA system outage performance optimization research and proposes an RS scheme.In multiple IRS-assisted uplink CR-NOMA systems,the channel gains of both PU and SU are optimized with the assistance of IRS,and RS is performed on SU alone,thereby improving the outage performance of SU.Subsequently,this thesis uses the asymptotic theorem to derive a closed expression for the SU outage probability,which largely helps to evaluate the SU outage performance,and reveals the influence of the target rate and transmit power allocation on the SU outage performance.In addition,this thesis analyzes the maximum achievable rate of SU in different decoding orders under the condition that PU outage performance is not affected.The simulation results show that this thesis clarifies in detail the improvement of SU outage performance under the RS scheme compared with the uplink CR-NOMA system without RS technology.