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In this letter, we propose a novel symbol-asynchronous non-orthogonal multiple access (ANOMA) scheme for downlink transmissions. First, ANOMA introduces an artificial symbol-offset between packets destined for different user equipment (UE) in order to reduce their mutual interference. Second, ANOMA adopts a pre-coding at the base station and a whitening-and-decomposing (WD) detection scheme at the receiving UE to simplify signal detection. With these two novel techniques, ANOMA can significantly enlarge the achievable rate region of the traditional non-orthogonal multiple access (NOMA). Moreover, the impact of pulse shape and symbol offset on the performance of ANOMA scheme are investigated in both Gaussian and Rayleigh block-fading channels. The numerical results show that ANOMA with precoding and WD detection outperforms asynchronous NOMA with successive interference cancellation detection, both outperform synchronous NOMA.
Cui et al. (Wed,) studied this question.