Comparison of Interference Cancellation Schemes for Non-Orthogonal Multiple Access System

Three potential interference cancellation schemes are compared for the application to a non-orthogonal multiple access communication system. One is the conventional successive interference cancellation (SIC) scheme based on independent single-user decodings. The other two, proposed in this paper, are a soft-in soft-out parallel interference cancellation (SISO-PIC) and a hybrid interference cancellation (HIC). The SISO-PIC is an improved joint iterative multi-user detection scheme, which has lower complexity than the prevalent multi-user detection. The HIC combines the above two schemes to permit users to be successively processed by a SISO-PIC window in the order of their power levels. A comprehensive comparison is given for these three schemes in aspects of error propagation, detection delay, and complexity when a practical channel code, repeat-accumulate code, is employed. Numerical results show that HIC is a trade-off scheme of the three aspects.