Massive machine type communication aims to support the connection of massive devices

which is still an important scenario in 6G. In this paper

a novel cluster-based massive access method is proposed for massive multiple input multiple output systems. By exploiting the angular domain characteristics

devices are separated into multiple clusters with a learned cluster-specific dictionary

which enhances the identification of active devices. For detected active devices whose data recovery fails

power domain nonorthogonal multiple access with successive interference cancellation is employed to recover their data via re-transmission. Simulation results show that the proposed scheme and algorithm achieve improved performance on active user detection and data recovery.