Sparse code multiple access (SCMA) building upon orthogonal frequency division multiplexing (OFDM) is a promising wireless technology for supporting massive connectivity in future machine-type communication networks. However, the sensitivity of OFDM to carrier frequency offset (CFO) poses a major challenge because it leads to orthogonality loss and incurs intercarrier interference (ICI). In this paper, we investigate the bit error rate (BER) performance of SCMA-OFDM systems in the presence of CFO over both Gaussian and multipath Rayleigh fading channels. We first model the ICI in SCMA-OFDM as Gaussian variables conditioned on a single channel realization for fading channels. The BER is then evaluated by averaging over all codeword pairs considering the fading statistics. Through simulations, we validate the accuracy of our BER analysis and reveal that there is a significant BER degradation for SCMA-OFDM systems when the normalized CFO exceeds 0.02.

翻译：基于正交频分复用（OFDM）的稀疏码多址接入（SCMA）是支持未来机器类通信网络中大规模连接的一种有前景的无线技术。然而，OFDM对载波频率偏移（CFO）的敏感性构成了重大挑战，因为它会导致正交性损失并引发载波间干扰（ICI）。本文研究了在高斯信道和多径瑞利衰落信道下存在CFO时SCMA-OFDM系统的误码率（BER）性能。我们首先将SCMA-OFDM中的ICI建模为以单个信道实现为条件的高斯变量（针对衰落信道）。随后，考虑衰落统计特性，通过对所有码字对进行平均来评估误码率。通过仿真，我们验证了误码率分析的准确性，并揭示了当归一化CFO超过0.02时，SCMA-OFDM系统会出现显著的误码率性能下降。