Simplified Random Access Design for Satellite Internet of Things with NOMA

Satellite Internet of Things (IoT) is a promising technical trend to tackle the ubiquitous connection requirements for 5G and beyond. In satellite IoT, the conventional random access scheme faces huge interaction overhead caused by the complicated signaling interactions and the large propagation delay of the satellite-ground link. To tackle this problem, we propose a simplified random access scheme. By utilizing the collision tolerance of non-orthogonal multiple access (NOMA) technology, random access and data transmission are integrated to reduce the overall interaction delay. At the transmitter side, the transmitted symbols are spread by the non-orthogonal sequence and the preamble corresponding to the non-orthogonal sequence. At the receiver side, the received signal is iteratively processed based on the minimum mean square error (MMSE) and serial interference cancellation (SIC). The simulation results show that the proposed scheme can reduce the transmission delay without losing the success rate of random access compared with the conventional scheme that only relies on preamble detection.