LLR calculation based on interference cancelation for non-orthogonal multiple access

Non-orthogonal multiple access improves spectral efficiency through sharing the same frequency resource with multiple wireless terminals. In the previous researches, it has been shown that a log likelihood ratio (LLR) calculated from a signal on the sharing spectrum should be masked to zero if the power of an interference signal is stronger than that of a desired signal. This implies that the spectrum is not shared by the terminal receiving the weaker signal. In this paper, a spectrum sharing scheme on the basis of interference cancelation and a LLR calculation with the probability density function of residual interference is proposed. Numerical results obtained thorough computer simulation show that the proposed scheme improves the performance by 1 dB at the BER of 10^-4 as compared to that of the conventional scheme.