Performance Analysis of NOMA System with QoS-Guarantee Scheme

With an objective of connecting everyone and everything in beyond 5th-generation and 6th-generation wireless communication systems, there is a need for scalability in the access network. Non-orthogonal multiple access (NOMA) is considered as one of the leading, prominent, and promising technology to provide a solution for massive connectivity with superior spectrum efficiency and user fairness. NOMA simultaneously serves multiple users in a single resource block, thereby resulting in unrestricted, however controlled inter-user interference. To detect users’ symbols, NOMA employs successive interference cancellation at the receiver. However, inter-user interference is unavoidable in NOMA and thus results in performance degradation. This work proposes a simple yet effective scheme for the downlink NOMA that guarantees users’ quality of service by minimizing inter-user interference. Closed-form expressions for outage probability under the assumption of imperfect channel state information (CSI) with hardware impairment (HI) are derived to facilitate the performance evaluation of the proposed scheme. Expression of outage probability for two users under the assumption of perfect CSI without HI is also presented. Monte Carlo simulations are used to validate the derived analytical expressions.