Performance Enhancement Using Receive Diversity With Power Adaptation in the NOMA System

This paper proposes receive diversity with power adaptation for a non-orthogonal multiple access (NOMA) system in a multi-user circumstance. Since the basic concept of power domain NOMA divides user data by the difference of power, successive interference cancellation (SIC) is necessary to extract user data. In the process of SIC calculation, the error propagation has occurred. Therefore, signal-to-interference-plus-noise ratio (SINR) decreases as the number of user entity increases in a power domain NOMA system. In order to mitigate the inter-user interference, data are allocated to subcarriers with an instantaneous user grouping scheme. With the subcarrier structure of the instantaneous user grouping scheme, this paper proposes receive diversity to improve the bit error rate (BER). However, since the diversity method decreases the sum capacity of the system, a power adaptation method is also proposed to compensate the sum capacity. The simulation results show that the proposed method improves the BER performance than the conventional scheme and increases sum capacity that is decreased by the receiver diversity scheme.