A Semi-Blind Receiver for Ambient Backscatter Communications with MPSK RF Source

Ambient backscatter communication (AmBC) is a promising technology for energy-and spectrum-efficient Internet of Things (IoT) communication. In an AmBC system, due to the strong direct link interference and the difficulty in acquiring the channel state information (CSI), the detection of IoT device symbol becomes difficult. In this paper, we propose a semi-blind receiver, which includes the semi-blind channel estimator and the direct-link-averaging detector (DL-AD). The semi-blind channel estimator only relies on two pilot symbols from the IoT device to indicate different CSI without the RF source pilots, and can eliminate the effect of the RF source symbols. The DL-AD is based on the log likelihood ratio test. The simulation results show that the semi-blind receiver has very similar error probability performance compared with the constellation learning (CL) receiver that we proposed earlier, and it is simpler than the CL receiver. We also propose an iterative version of the semiblind receiver that has improved performance as shown in simulations.