  Backscatter communication (BC) is a promising technique for future
Internet-of-Things (IoT) owing to its low complexity, low cost, and potential
for energy-efficient operation in sensor networks. There are several network
infrastructure setups that can be used for BC with IoT nodes. One of them is
the bistatic setup where typically there is a need for high dynamic range and
high-resolution analog-to-digital converters at the reader. In this paper, we
investigate a bistatic BC setup with multiple antennas. We propose a novel
transmission scheme, which includes a protocol for channel estimation at the
carrier emitter (CE) as well as a transmit beamformer construction that
suppresses the direct link interference between the two ends of a bistatic link
(namely CE and reader), and increases the detection performance of the
backscatter device (BD) symbol. Further, we derive a generalized log-likelihood
ratio test (GLRT) to detect the symbol/presence of the BD. We also provide an
iterative algorithm to estimate the unknown parameters in the GLRT. Finally,
simulation results show that the required dynamic range of the system is
significantly decreased, and the detection performance of the BD symbol is
increased, by the proposed algorithm compared to a system not using beamforming
at the CE.
