An Error Rate Comparison of Power Domain Non-Orthogonal Multiple Access and Sparse Code Multiple Access

• Main Authors: Qu Luo, Pengyu Gao, Zilong Liu, Lixia Xiao, Zeina Mheich, Pei Xiao, Amine Maaref
• Format: Article
• Language: English
• Published: IEEE 2021-01-01
• Series: IEEE Open Journal of the Communications Society
• Subjects: Non-orthogonal multiple access (NOMA); power domain NOMA (PD-NOMA); successive interference cancellation (SIC); generalized sphere decoder (GSD); sparse code multiple access (SCMA); bit error rate (BER)
• Online Access: https://ieeexplore.ieee.org/document/9372309/

Non-orthogonal Multiple Access (NOMA) has been envisioned as one of the key enabling techniques to fulfill the requirements of future wireless networks. The primary benefit of NOMA is higher spectrum efficiency compared to Orthogonal Multiple Access (OMA). This paper presents an error rate comparison of two distinct NOMA schemes, i.e., power domain NOMA (PD-NOMA) and Sparse Code Multiple Access (SCMA). In a typical PD-NOMA system, successive interference cancellation (SIC) is utilized at the receiver, which however may lead to error propagation. In comparison, message passing decoding is employed in SCMA. To attain the best error rate performance of PD-NOMA, we optimize the power allocation with the aid of pairwise error probability and then carry out the decoding using generalized sphere decoder (GSD). Our extensive simulation results show that SCMA system with &#x201C;<inline-formula> <tex-math notation="LaTeX">$5\times 10$ </tex-math></inline-formula>&#x201D; setting (i.e., ten users communicate over five subcarriers, each active over two subcarriers) achieves better uncoded BER and coded BER performance than both typical &#x201C;<inline-formula> <tex-math notation="LaTeX">$1\times 2$ </tex-math></inline-formula>&#x201D; and &#x201C;<inline-formula> <tex-math notation="LaTeX">$2\times 4$ </tex-math></inline-formula>&#x201D; PD-NOMA systems in uplink Rayleigh fading channel. Finally, the impacts of channel estimation error on SCMA, SIC and GSD based PD-NOMA and the complexity of multiuser detection schemes are also discussed.