Definition of system parameters.

Short-packet communication (SPC) is a key enabler for ultra-reliable low-latency communication (URLLC) in next-generation wireless networks. In this paper, we investigate the block error rate (BLER) performance of a reconfigurable intelligent surface (RIS)-assisted ambient backscatter communication (AmBC) system operating under a non-orthogonal multiple access (NOMA) framework. Different from existing works, our study considers a Nakagami-m fading environment and derives closed-form expressions for the average and asymptotic BLER. By leveraging power-domain NOMA and RIS-assisted reflection, we optimize signal reception for both direct and backscattered links, enhancing spectral efficiency and communication reliability. Numerical and Monte Carlo simulation results validate our analytical findings, demonstrating significant performance gains in terms of BLER reduction and system throughput improvement. These results highlight the potential of RIS-assisted AmBC-NOMA systems in enabling efficient SPC for URLLC applications.短数据包通信（Short-packet communication，SPC）是下一代无线网络实现超可靠低延迟通信（Ultra-reliable low-latency communication，URLLC）的关键支撑技术。本文针对非正交多址接入（Non-orthogonal multiple access，NOMA）架构下的可重构智能表面（Reconfigurable intelligent surface，RIS）辅助环境反向散射通信（Ambient backscatter communication，AmBC）系统，研究其块错误率（Block error rate，BLER）性能。与现有研究不同，本文考虑Nakagami-m衰落（Nakagami-m fading）信道环境，推导得到平均块错误率与渐近块错误率的闭式表达式。通过利用功率域非正交多址接入与RIS辅助反射技术，本文对直射链路与反向散射链路的信号接收进行优化，提升了频谱效率与通信可靠性。数值分析与蒙特卡洛仿真结果验证了本文的理论分析结论，表明该系统在降低块错误率与提升系统吞吐量方面具有显著性能增益。上述结果凸显了RIS辅助AmBC-NOMA系统在为URLLC应用提供高效SPC服务方面的应用潜力。