  Backscatter communication (BC) has emerged as a key technology to satisfy the
increasing need for low-cost and green Internet-of-Things (IoT) connectivity,
especially in large-scale deployments. Unlike the monostatic BC (MoBC), the
bistatic BC (BiBC) has the possibility to decrease the round-trip path loss by
having the carrier emitter (CE) and the reader in different locations.
Therefore, this work investigates the BiBC in the context of cell-free
multiple-input multiple-output (MIMO) networks by exploring the optimal
selection of CE and reader among all access points, leveraging prior knowledge
about the area where the backscatter device (BD) is located. First, a maximum a
posteriori probability (MAP) detector to decode the BD information bits is
derived. Then, the exact probability of error for this detector is obtained. In
addition, an algorithm to select the best CE-reader pair for serving the
specified area is proposed. Finally, simulation results show that the error
performance of the BC is improved by the proposed algorithm compared to the
benchmark scenario.
