A Generalized STAR-RIS-Empowered Ambient Backscatter Short-Packet Communication Systems With Partial NOMA

This letter proposes a simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS)-empowered ambient backscatter short-packet paradigm with partial non-orthogonal multiple access (p-NOMA). In this paradigm, a multi-antenna base station communicates with users using finite blocklength schemes to achieve low latency transmission while flexibly exploiting the spectrum utilization via p-NOMA. Considering Nakagami–m fading channels, discrete phase-shift alignment, and imperfect successive interference cancellation, we provide a generalized information-theoretic framework that characterizes passive, active, and hybrid STAR-RIS types, to measure the block-error rate (BLER) and goodput. To gain useful insights into system designs, an upper-bound BLER at high transmit power has been derived. Numerical results demonstrate the BLER superiority of p-NOMA over its orthogonal multiple access (OMA) and NOMA counterparts, as well as the respective twofold and fourfold enhancements in terms of goodput.