Two-Tier Power Allocation for Non-Orthogonal Multiple Access Based Cognitive Radio Networks

摘要

One of the most challenging issues in non-orthogonal multiple access (NOMA) based cognitive radio networks (CRNs) is the power allocation (PA) problem. Moreover, the quality of service (QoS) constraints of both the primary and secondary users can not be neglected when dealing with the PA problem. In this paper, a two-tier PA algorithm is proposed for NOMA-based CRNs to make the best use of the inherited characteristics of power domain based NOMA technique. Specifically, the proposed algorithm is able to solve the PA problem in NOMA-based CRNs under primary user (PU) QoS constraints through setting up an overall power constraint for the secondary users (SUs), this represents the first tier. Additionally, the PA among the SUs, representing the second tier, is accomplished based on their channel gains. The performance of the proposed PA approach with NOMA-based CRNs is compared with the fractional transmit power control technique which is implemented typically in conventional orthogonal multiple access based CRNs, in terms of the number of admitted SUs and the outage probability. The simulation results have confirmed the superiority of NOMA-based networks compared to their OMA counterparts due to the much better PA in NOMA-based CRNs compared to OMA-based ones.