Iterative Multiuser Detection and Decoding for Sparse Code Multiple Access Combined with Spectrally Efficient Frequency Division Multiplexing

Sparse code multiple access (SCMA) combined with spectrally efficient frequency division multiplexing (SEFDM) is a wireless air-interface technology with dual non-orthogonal characteristic which can meet the high spectral efficiency requirement of the future Internet of Things (IoT). In this paper, an iterative multiuser detection/decoder (IMUDD) method for SCMA-SEFDM is proposed, which performs soft information iteration in a turbo style. IMUDD can effectively achieve the multiple-access interference (MAI), inter-symbol interference (ISI) and inter-carrier interference (ICI) cancellation through an external iteration and three internal iterative processes. At each iteration, extrinsic information is extracted from detection and decoding stages, then it is used as a priori information in the next iteration. Furthermore, to reduce the computational complexity of IMUDD scheme, a logarithm domain IMUDD is adopted and analyzed. The simulation results show that IMUDD has a noticeable performance improvement compared to the traditional turbo structured receivers over the multipath fading channel or the additive white Gaussian noise (AWGN) channel.