  This article considers the massive MIMO unsourced random access problem on a
quasi-static Rayleigh fading channel. Given a fixed message length and a
prescribed number of channel uses, the objective is to construct a coding
scheme that minimizes the energy-per-bit subject to a fixed probability of
error. The proposed scheme differs from other state-of-the-art schemes in that
it blends activity detection, single-user coding, pilot-aided and temporary
decisions-aided iterative channel estimation and decoding, minimum-mean squared
error (MMSE) estimation, and successive interference cancellation (SIC). We
show that an appropriate combination of these ideas can substantially
outperform state-of-the-art coding schemes when the number of active users is
more than 100, making this the best performing scheme known for this regime.
