RFF Based Detection for SCMA in Presence of PA Nonlinearity

Abstract

The next-generation of communication systems must be capable of serving a significantly higher traffic generated by a large number of devices. To support massive connectivity over limited time-frequency resources, several non-orthogonal multiple access (NOMA) paradigms have emerged. In this context, sparse code multiple access (SCMA) based NOMA is particularly attractive due to its robustness to error-propagation, and its potentially high coding-gain with appropriate codebook design. However, the performance of SCMA based systems is severely degraded by distortions introduced by non-ideal hardware, e.g. power-amplifier (PA) nonlinearity. To mitigate such artefacts, in this letter, a random Fourier feature (RFF) based hybrid message passing algorithm (MPA) is proposed, and validated through computer simulations. Lastly, an analytical proof is presented that indicates that the use of RFFs significantly improves the convergence of the MPA in the presence of impairments, and renders error-rate performance equivalent to that of a linear Gaussian channel under approximate MPA.