Concurrent Transmission for Low-Power Symbiotic Backscatter Communications: Spatial Modulation and Detector Design

Backscatter communication, which enables a battery-free backscatter tag to transmit information by using incident radio frequency (RF) signal as the carrier, is a promising solution for future green Internet of Things. In this paper, we consider a symbiotic backscatter communication system with multiple tags, in which the multi-antenna tags employ spatial modulation for concurrent transmission to improve spectral efficiency. We propose a joint message-passing detector to recover both the RF source signal and the multiple tag signals simultaneously. Simulation results verify that the proposed algorithm achieves better bit error rate performance, compared with the existing detection algorithm based on successive interference cancellation.