Non-orthogonal access scheme based on interference cancelation and log-likelihood weighting with LDPC code

Non-orthogonal access improves the 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 a 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 LLR weighting to reduce the effect of interference in low density parity check (LDPC) decoding is proposed. Numerical results obtained thorough computer simulation show that the proposed scheme improves the performance by 2dB at the BER of 10^-2 as compared to that of the system without weighting and overlapping to the parity bits is less sensitive to the BER performance relative to the case for overlapping to the systematic bits.