A Fast and Efficient User Pairing and Power Allocation Algorithm for Non-orthogonal Multiple Access in Cellular Networks

Non-orthogonal multiple access (NOMA) is emerging as a promising multiple access technology for the 5th generation cellular networks to address the fast growing mobile data traffic. It applies superposition coding in transmitters, allowing simultaneous allocation of the same frequency resource to multiple intra-cell users. Successive interference cancellation is used at the receivers to cancel intra-cell interference. User pairing and power allocation (UPPA) is a key design aspect of NOMA. Existing UPPA algorithms are mainly based on exhaustive search method with extensive computation complexity, which can severely affect the NOMA performance. In this paper we propose a fast proportional fairness (PF) scheduling based UPPA algorithm to address the problem. The novel idea is to form user pairs around the users with the highest PF metrics with pre-configured fixed power allocation. System level simulation results show the proposed algorithm is significantly faster (7 times faster for the scenario with 20 users) with a negligible throughput loss than the existing exhaustive search algorithm.