Joint User Grouping and Decoding Order in Uplink/Downlink MISO/SIMO-NOMA

In this paper, we design and investigate a novel uplink/downlink (UL/DL) non-orthogonal multiple access (NOMA) network using a common relay. Instead of successive interference cancellation (SIC) for UL/DL NOMA systems with fixed decoding order based on the statistical channel state information (CSI), we adopt the dynamic decoding order according to power level of received signals. Specifically, by exploiting the CSI-based dynamic decoding order, better fairness can be achieved and applicable. This decoding scheme is highly suitable for implementing a NOMA system in practice. The closed-form expressions for the users' outage probabilities are derived, and then an asymptotic analysis is carried out. Insightful discussions with diversity order are provided. Simulations are performed to corroborate the exactness of the theoretical analysis.