Blind Signal Classification Analysis and Impact on User Pairing and Power Allocation in Nonorthogonal Multiple Access

This paper studies blind signal classification (SC) in the nonorthogonal multiple access (NOMA) system, which especially determines whether or not the received NOMA signal requires successive interference cancellation (SIC) without a priori signal information. In this paper, two types of blind SC errors are analyzed: 1) the signal that has to cancel the superposed interference component is classified as one that does not require SIC and 2) the signal that has no need of performing SIC is classified as one that requires SIC. Here, the interesting observation is that the classification error of the first type decreases with the SNR, but that of the second type increases with the SNR. In this regard, this paper proposes the joint user pairing and power allocation policy for the NOMA system based on the above observation that the blind SC performance of the NOMA user who does not perform SIC decreases with the SNR. The joint optimization problem maximizes the sum-rate gain of NOMA over orthogonal multiple access (OMA) with constraints on the maximum classification error probability and the minimum data rate. Since the problem is nonconvex, we propose the numerical algorithm that iteratively finds the appropriate user scheduling and power allocation. Simulation results show that the proposed scheme outperforms existing user scheduling methods.