Abstract

Non-orthogonal Multiple Access (NOMA) enhances system radio capacity and offers superior spectral efficiency. However, the intricacy of Successive Interference Cancellation (SIC) poses a significant challenge for NOMA implementation. To address this, dividing users into orthogonal frequency groups and employing hybrid NOMA within each group is recommended. Our simulation results for single-carrier NOMA (SC-NOMA) sum rate analysis demonstrate that increasing the number of users beyond a certain threshold leads to a decline in network sum throughput. Consequently, it’s not feasible to indefinitely increase the number of users per carrier. Furthermore, we investigated user pairing strategies within the hybrid NOMA framework. Our simulation results for Near-Near (N-N), far-far (F-F), and near-far (N-F) user pairing schemes demonstrate that user pairing can significantly reduce computational costs. To further evaluate network sum rate performance, we compared these pairing schemes using both SC-NOMA and Time Division Multiple Access (TDMA) over a Nakagami-m fading channel. Our findings show that pairing the nearest user with the farthest user dramatically increases the total sum rate. While NOMA still outperforms TDMA with respect to sum rate when using N-N and F-F pairings, the improvement is less pronounced. SC-NOMA, on the other hand, underperforms TDMA. At low Signal-to-Noise Ratios (SNR), N-N, F-F pairing yields a higher sum rate than N-F pairing. However, this trend reverses at high SNR, where N-F pairing offers a superior sum rate. Consequently, N-F pairing can also lead to increased sum rates at high SNR.

Authors

Keerti Tiwari
Capgemini Engineering, Bangalore, India

Keywords

Hybrid NOMA, SC-NOMA, TDMA, User Pairing, Sum-Rate, Outage, Nakagami-M Fading Channel