A RIS-Segmented Symbiotic Ambient Backscatter Communication System

This article proposes a reconfigurable intelligent surface (RIS) segmented symbiotic ambient backscatter system, which is composed of a primary source (S), a RIS, and a cooperative receiver (D) that decodes the signals from S and RIS with the aid of successive interference cancellation (SIC). For such, the RIS is segmented into two zones, namely, an EP zone and a BD zone, where the EP zone is used to enhance the received primary signal at D while the BD zone is utilized to backscatter RIS's signal to D. The coexistence outage probability (COP) is first developed, which is shown to be dominated by the minimum number of reflectors in the two zones for sufficiently high transmit signal-to-noise ratio (SNR). In contrast, the sum ergodic capacity (EC) can only be improved by increasing the transmit power and the number of reflectors in the EP zone at high transmit SNR. Finally, two algorithms are designed to minimize the number of reflectors in the two zones while achieving acceptable COP or sum EC.