  We generalize the type-based multiple access framework proposed by Mergen and
Tong (2006) to the case of unsourced multiple access. In the proposed
framework, each device tracks the state of a physical/digital process,
quantizes this state, and communicates it to a common receiver through a shared
channel in an uncoordinated manner. The receiver aims to estimate the type of
the states, i.e., the set of states and their multiplicity in the sequence of
states reported by all devices. We measure the type estimation error using the
Wasserstein distance. Considering an example of multi-target position tracking,
we show that type estimation can be performed effectively via approximate
message passing. Furthermore, we determine the quantization resolution that
minimizes the type estimation error by balancing quantization distortion and
communication error.
