Receiver and resource allocation optimization for uplink NOMA in 5G wireless networks

Non-Orthogonal Multiple Access (NOMA) is a promising multiple access technique for 5G wireless networks. In uplink NOMA, more than one user can use the same subcarrier, which increases the system throughput and fairness. Due to the non-orthogonality among the users, joint processing is required at the receiver to retrieve the users´ signals. In this paper, we propose solutions to optimize the receiver and the radio resource allocation of uplink NOMA. First, we propose an iterative multiuser detection and decoding (MUDD) to improve the performance of the multiuser detector by utilizing the information derived by the channel decoder. In addition, a novel subcarrier and power allocation algorithm is proposed for NOMA scheme that maximizes the users´ weighted sum-rate. The link-level performance evaluation has shown that the proposed iterative MUDD approach brings about 4.5 dB and 9.8 dB performance improvements at block error rate equal to 10^-2 comparing to conventional multiuser detection, for QPSK and 16QAM modulations, respectively. Furthermore, the system-level results show that the proposed resource allocation algorithm achieves the system spectral efficiency upper-bound, making NOMA significantly outperforms OFDMA in terms of spectral efficiency and fairness.