Power Allocation of Two-User Downlink Channel Decoding

This paper investigates an efficient power allocation for channel decoding algorithms in two-user downlink non-orthogonal multiple access (NOMA). We consider three successive interference cancellation (SIC) algorithms with low-density parity-check (LDPC) codes, i.e., the SIC treats interference as noise (N-SIC) algorithm, the SIC treats modulation of interference signal as auxiliary information (J-SIC), and the SIC exchanges the external decoding information of the signals for two users (E-SIC). To improve the decoding accuracy, we propose power allocation algorithms for SIC decoding based on fairness index and outage probability respectively. The rate-fairness of users is also optimized. Simulation results show that the iterative E-SIC can achieve a significant performance gain over N-SIC and J-SIC, and this gain is much smaller when the power allocation (PA) is used in the three SIC decodings. Moreover, we analyze performance bound of Polyanskiy-Poor-Verdu (PPV) finite-length for the SIC decodings. It provides a theoretical analysis for the optimization of frame error rate (FER) by power allocation.