BER Performance of Time-Asynchronous Uplink NOMA

We consider an asynchronous transmission scenario for uplink non-orthogonal multiple access (NOMA) model, where K users transmit their message to a base station (BS) with equal transmission power and certain time offsets. We propose an Asynchronous-NOMA which reduces the mutual interference between users compared with conventional synchronous Power-Domain NOMA. We also propose a constellation design based on our system model and maximum likelihood detection aided successive interference cancellation (ML-SIC) is applied to decode the message of each user. We evaluate the performance of the system by deriving the bit error rate (BER) of the output. Simulation results show the BER is reduced given the proposed asynchronous scheme.