Energy Detection for Reflecting Surfaces-Aided Ambient Backscatter Communications

This paper considers a reflecting surface (RS)-aided ambient backscatter communication (AmBC) system, where the RS can be either an intelligent RS (IRS) or a dumb RS (DRS). The former uses channel state information to apply phase shifts and form beams towards the reader, while the latter randomly reflects signals without applying phase shifts. The paper aims to evaluate the effects of ambient sources that act as simultaneous energy and interference sources, as well as the potential benefits of RSs on the bit error rate (BER) performance and coverage of AmBC systems. Therefore, it presents accurate BER expressions for on-off keying modulation using a simple non-coherent energy detection scheme under an IRS with ideal/non-ideal phase shifts and a DRS. Numerical and Monte-Carlo simulation results demonstrate that an IRS under both ideal and non-ideal phase shifts outperforms a DRS; however, the latter is cost-efficient and suitable for low-power applications, such as Internet of things communications. The results also show that an RS significantly enhances the limited coverage of conventional AmBC systems. Finally, it is observed that potential blockages limit the BER in the high-signal-to-noise ratio and large number of reflecting elements regimes, which can be improved by increasing the number of antennas.