  In next generation Internet-of-Things, the overhead introduced by grant-based
multiple access protocols may engulf the access network as a consequence of the
unprecedented number of connected devices. Grant-free access protocols are
therefore gaining an increasing interest to support massive access from
machine-type devices with intermittent activity. In this paper, coded random
access (CRA) with massive multiple input multiple output (MIMO) is investigated
as a solution to design highly-scalable massive multiple access protocols,
taking into account stringent requirements on latency and reliability. With a
focus on signal processing aspects at the physical layer and their impact on
the overall system performance, critical issues of successive interference
cancellation (SIC) over fading channels are first analyzed. Then, SIC
algorithms and a scheduler are proposed that can overcome some of the
limitations of the current access protocols. The effectiveness of the proposed
processing algorithms is validated by Monte Carlo simulation, for different CRA
protocols and by comparisons with developed benchmarks.
