Coded Random Access for 6G: Intra-Frame Spatial Coupling with ACKs

A massive multiple access scheme, capable of serving a large number of uncoordinated devices while fulfilling reliability and latency constraints, is proposed. The scheme belongs to the class of coded random access protocols and is tailored to massive multiple input multiple output (MIMO) base station processing. It achieves high reliability owing to an intra-frame spatial coupling effect, obtained by a simple device access protocol combined with acknowledgements (ACKs) from the base station. The proposed scheme is particularly interesting to address the challenges of massive machine-type communications in the framework of the future 6G systems.