Cell-edge users of future cellular internet of things (IoT) sensor networks can suffer from extremely severe channel conditions, especially under mobility with high speeds, i.e., doubly selective channels. This paper presents a performance improvement method for IoT cell-edge users downlink transmission under doubly selective channels. To this end, we consider the implementation of multi-carrier modulation (MCM)-based cooperative user relaying non-orthogonal multiple access (CUR-NOMA) combined with two interference cancellation schemes and derive the lower bound of the E2E-BER of the proposed scheme. The obtained results showed that the proposed scheme requires a low computational complexity and significantly improves the systems performance even if the channel state information (CSI) is imperfect.