A BER Analysis of NOMA on Rician Fading Channels

Non-Orthogonal Multiple Access (NOMA) has been a hot research topic over the past years. The general trend in the NOMA literature is the so-called Power-Domain NOMA (PD-NOMA), which requires a strong power imbalance at the receiver between the superposed signals. Also, the focus in the literature has been on the derivation of information theoretic results, and practical bit error rate (BER) has not attracted much attention. In recent papers, some of the present authors revived an early NOMA concept, which we refer to as NOMA-2000. Performance of NOMA-2000 was investigated on AWGN channels and Rayleigh fading channels, and it was found that in most cases this technique significantly outperforms PD-NOMA. The purpose of this paper is to compare the BER performances of the two schemes on Rician fading channels, which provide a more accurate representation of the radio channel in dense urban environments. The results confirm that on Rician channels too PD-NOMA suffers a strong SNR degradation with static resource allocation and that NOMA-2000 provides substantially better performance. But with dynamic resource allocation and user pairing, both techniques achieve good performance as long as the channel overloading factor does not exceed some limit.