Iterative Water-Filling Power and Subcarrier Allocation for Multicarrier NOMA Downlink

Abstract

Novel closed form formulae of iterative optimal power control and allocation, and criterion for optimal subcarrier allocation are derived for downlink of multicarrier non-orthogonal multiple access (MC-NOMA) systems. For the first time, we present closed form water-filling formulae that quantify exactly the following effects of multiple access interference for optimal power allocation of MC-NOMA downlink: (i) Each user should take into account the sum of interference from other stronger users plus the receiver Gaussian noise as an equivalent interference in each subcarrier; (ii) The sum of each user's interference to other weaker users should be accounted as factors which determine the distinct water levels in each subcarrier of each of the other weaker users. We also propose novel iterative water-filling algorithm and projected conjugate gradient algorithm that facilitate iterative computation of optimal power allocation for MC-NOMA downlink.