Ambient Backscatter Communication Systems: Capacity and Outage Performance Analysis

Ambient backscatter is an emerging green communication technology that exploits the environmental radio frequency (RF) signals to enable passive devices to communicate with each other. This paper investigates channel capacity and outage performance of ambient backscatter communication systems. Specifically, a calculation method is proposed to facilitate capacity analysis, and the ambient backscatter system capacities are derived in the case of four different RF signals. It is surprisingly found that the channel capacity is obtained when the RF signals are not equiprobably backscattered by tag, and that the capacity with complex Gaussian RF signals is not exactly twice that with real ones for the ambient backscatter communication systems. Then, the outage probability and its asymptotic value in the high signal-to-noise ratio regime are obtained. Since the exact outage expression consists of an infinite number of terms, a tight truncation error bound is derived to reasonably estimate the number of effective terms for numerical simulation. Finally, simulation results are provided to corroborate theoretical analysis.