Performance Analysis of NOMA-Based Spectrum Sharing System With Imperfect SIC

Abstract

This paper presents a non-orthogonal multiple access (NOMA)-based spectrum sharing scheme with imperfect successive interference cancellation (i-SIC), where the secondary user assists the primary to achieve cooperative multiplexing. The proposed scheme allows primary and secondary transmitters to transmit in alternate time slots and, hence, no primary transmitter's (PT) interference at the secondary receiver (SR). However, since the relay node and secondary transmitter (ST) are transmitting simultaneously on the same frequency spectrum, ST causes interference to the primary user. Therefore, the proposed scheme imposes the variable interference threshold constraint (v-ITC) to ST transmit power to improve the performance of both primary and secondary networks. We derive the closed-form expressions for the outage probability and ergodic rate of the proposed system. Furthermore, numerical results are presented to manifest the advantages of the v-ITC scheme on outage performance and the ergodic rate of the secondary network (SN).