Ambient Backscatter Communications Systems Using MFSK Modulation

In this paper, we propose a novel M-ary frequency shift keying (MFSK) modulation scheme for the Tag in ambient backscatter communications system. Leveraging on the frequency shifting feature of the MFSK modulation, the direct interference from the ambient RF signal is removed with the assistance of a set of band-pass filters. A simple energy detector is proposed for symbol detection according to the post-filter signals. Closed-form expressions for the symbol error rate (SER) and outage probability of the system are derived, based on which, the modulation order, operating signal-to-noise ratio (SNR), and the tag location is optimized. The findings of the paper suggest that the impact of modulation order on the SER performance depends heavily on the operating SNR, and the optimal modulation order exhibits a binary behavior.