Group Based Spreading and Symbol Puncturing Design for NOMA Systems

In this paper, we propose a flexible group-based signature shared access (GSSA) NOMA transmission scheme that spreading length and number of maximum multiplexed users are parameterized. Because the SINR is in an in-direct relationship with the increasing number of multiplexed users, we show that combination of symbol puncturing at the transmitter and ML-DF at the receiver can be an effective solution to lower both BLER and receiver complexity for handling large number of multiplexed uplink users. The proposed NOMA design for IIoT uplink offers a good trade-off point between higher spectral efficiency and high performance (reliability) with low complex multi-user iterative receiver.