  We introduce a modulation for unsourced massive random access whereby the
transmitted symbols are rank-1 tensors constructed from Grassmannian
sub-constellations. The use of a low-rank tensor structure, together with
tensor decomposition in order to separate the users at the receiver, allows a
convenient uncoupling between multi-user separation and single-user demapping.
The proposed signaling scheme is designed for the block fading channel and
multiple-antenna settings, and is shown to perform well in comparison to
state-of-the-art unsourced approaches.
