A STAR-RIS-Segmented Parasitic AmBC System

In this paper, we present a simultaneous transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) segmented parasitic ambient backscatter system, where the STAR-RIS is composed of an enhancing primary signal (EP) zone and a backscatter device (BD) zone. It is proposed to adaptively adjust the transmit power of the source instead of the transmission/reflection coefficients of the STAR-RIS to guarantee the concurrent transmission of the primary system and backscatter system, realizing a low-power and low-complexity STAR-RIS. To evaluate the overall transmission reliability of the considered parasitic system, we derive the closed-form expressions for the coexistence outage probability (COP) under three typical coverage scenarios. Moreover, the transmit power constraint at source is also considered and the corresponding COP is then derived . Both analytical and numerical results show that the proposed power-adaptive system has a superior COP performance to that of the fixed power setup. Additionally, a larger transmit power limit at the source leads to a superior COP performance.