Iterative Clipping Noise Elimination of Clipped and Filtered SCMA-OFDM System

Similar to conventional orthogonal frequency division multiplexing (OFDM) signal, the signals of sparse code multiple access combine with orthogonal frequency division multiplexing (SCMA-OFDM) existing the problem that its peak-to-average power ratio (PAPR) is unbearable high. In this paper, the clipping method is adopted to reduce the PAPR of the SCMA-OFDM signal. However, the clipping process brings extra noise to the SCMA-OFDM signal while the clipping noise is not taken into account in the message passing algorithm (MPA), which makes the MPA detection inaccurate and leads to a phenomenon that the decoding performance declines sharply with the increasing of E
_b
/N
₀
. Moreover, due to the distortion of SCMA-OFDM signals caused by clipping process, the system bit error rate (BER) performance degrades obviously. To tackle the issues above, we analyze the random characteristics of the clipping noise for the MPA detection scheme. Then, an iterative clipping noise elimination scheme is proposed to restore the BER performance of clipped SCMA-OFDM system. Simulation results show that our method can remove the phenomenon that the BER performance declines sharply at the high E
_b
/N
₀
region and the proposed iterative clipping noise elimination scheme restores the BER performance significantly.