CDF-Based Scheduling for Uplink Non-Orthogonal Multiple Access

In order to exploit the multiuser diversity in uplink non-orthogonal multiple access (NOMA) systems, we adopt the concept of the cumulative distribution function (CDF)-based scheduling for NOMA, which can fully exploit the multiuser diversity while providing fair resource sharing among the users. To support the simultaneous transmissions of multiple users with NOMA, we propose two user scheduling algorithms named CS- NOMA and CS-NOMA-Group. With CS-NOMA, in each slot the two users with the largest CDF values of their channel gains are selected. On the other hand, with CS-NOMA-Group, the users are first separated by two groups where one group consists of the users having relatively better channel gains on the average sense while the remaining users form another group. Then, in each slot, the user showing the largest CDF value of channel gain is selected in each group. For both CS-NOMA and CS- NOMA-Group, we additionally introduce a power allocation algorithm for the selected two users in each slot to balance the data rates of the two users. Through extensive simulations, we show the superior performance of CS-NOMA and CS-NOMA-Group against the conventional CS.