Recent advances in the communication systems culminated in a new class of multiple access schemes, named non-orthogonal multiple access (NOMA), where the main goal is to increase the spectrum efficiency by overlapping data from different users in a single time-frequency resource used by the physical layer. NOMA receivers can resolve the interference among data symbols from different users, increasing the overall system spectrum efficiency without introducing symbol error rate (SER) performance loss, which makes this class of multiple access techniques interesting for future mobile communication systems. This paper analyzes one promising NOMA technique, called sparse code multiple access (SCMA), where C users can share U<C time-frequency resources from the physical layer. Initially, the SCMA and orthogonal frequency division multiplexing (OFDM) integration is considered, defining a benchmark for the overall SER performance for the multiple access technique. Furthermore, this paper proposes the SCMA and generalized frequency division multiplexing (GFDM) integration. Since GFDM is a highly flexible non-orthogonal waveform that can mimic several other waveforms as corner cases, it is an interesting candidate for future wireless communication systems. This paper proposes two approaches for combining SCMA and GFDM. The first one combines a soft equalizer, called block expectation propagation (BEP), and a multi-user detection (MUD) scheme based on the sum-product algorithm (SPA). This approach achieves the best SER performance, but with the significant increment of the complexity at the receiver. In the second approach, BEP is integrated with a simplified MUD, which is an original contribution of this paper, aiming for reducing the receiver’s complexity at the cost of SER performance loss. The solutions proposed in this paper show that SCMA-GFDM can be an interesting solution for future mobile networks.

通信系统的最新进展最终导致了一种新的多址方案，称为非正交多址（NOMA），其主要目标是通过在一个单一的时频资源中重叠来自不同用户的数据来提高频谱效率。通过物理层。NOMA接收器可以解决来自不同用户的数据符号之间的干扰，从而提高整体系统频谱效率，而不会引起符号错误率（SER）性能损失，这使此类多址技术对于未来的移动通信系统很有意义。本文分析了一种有前途的NOMA技术，称为稀疏代码多路访问（SCMA），其中C用户可以共享U < C来自物理层的时频资源。最初，考虑了SCMA和正交频分复用（OFDM）集成，从而为多址技术的整体SER性能定义了基准。此外，本文提出了SCMA和广义频分复用（GFDM）集成。由于GFDM是一种高度灵活的非正交波形，可以作为拐角情况模仿其他几个波形，因此它是未来无线通信系统的一个有趣候选。本文提出了两种结合SCMA和GFDM的方法。第一个结合了称为块期望传播（BEP）的软均衡器和基于和积算法（SPA）的多用户检测（MUD）方案。这种方法可实现最佳的SER性能，但是随着接收器复杂度的显着增加。在第二种方法中，BEP与简化的MUD集成在一起，这是本文的原始贡献，旨在以SER性能损失为代价降低接收机的复杂性。本文提出的解决方案表明，SCMA-GFDM可以成为未来移动网络的有趣解决方案。